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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
384872
2Even Fibonacci numbers
318161
3Largest prime factor
232543
4Largest palindrome product
211509
5Smallest multiple
224824
6Sum square difference
226516
710001st prime
194192
8Largest product in a series
171885
9Special Pythagorean triplet
169925
10Summation of primes
155691
11Largest product in a grid
116898
12Highly divisible triangular number
105950
13Large sum
112543
14Longest Collatz sequence
110436
15Lattice paths
91949
16Power digit sum
115366
17Number letter counts
75906
18Maximum path sum I
74290
19Counting Sundays
68558
20Factorial digit sum
104915
21Amicable numbers
73686
22Names scores
68841
23Non-abundant sums
51805
24Lexicographic permutations
59475
251000-digit Fibonacci number
80477
26Reciprocal cycles
42417
27Quadratic primes
44725
28Number spiral diagonals
59087
29Distinct powers
53705
30Digit fifth powers
56990
31Coin sums
42233
32Pandigital products
36305
33Digit canceling fractions
37451
34Digit factorials
49661
35Circular primes
45402
36Double-base palindromes
48219
37Truncatable primes
38479
38Pandigital multiples
32703
39Integer right triangles
37872
40Champernowne's constant
42362
41Pandigital prime
35407
42Coded triangle numbers
40474
43Sub-string divisibility
30197
44Pentagon numbers
29083
45Triangular, pentagonal, and hexagonal
38442
46Goldbach's other conjecture
31026
47Distinct primes factors
29677
48Self powers
63913
49Prime permutations
29442
50Consecutive prime sum
31648